The strong growth in demand for portable consumer electronics is driving the need for high-capacity storage devices. Non-volatile semiconductor memory devices, such as flash memory storage cards, are widely used to meet the ever-growing demands on digital information storage and exchange. Their portability, versatility and rugged design, along with their high reliability and large capacity, have made such memory devices ideal for use in a wide variety of electronic devices, including for example digital cameras, digital music players, video game consoles, PDAs and cellular telephones.
Semiconductor memory may be provided within a semiconductor package, which protects the semiconductor memory and enables communication between the memory and a host device. Examples of semiconductor packages include system-in-a-package (SiP) or multichip modules (MCM), where a plurality of die are mounted and interconnected on a small footprint substrate. The die in the stack are typically wire bonded to each other and the substrate to allow signal exchange to/from select die in the die stack.
Conventional wire bonding techniques form a loop from a die bond pad on one die to a die bond pad on the next adjacent die, and repeating the process up the entire die stack and across all die bond pads on each die. Conventional bonding techniques form wire bond loops to a height of over 120 μm. As the number of semiconductor die in a die stack increase, the height of the wire bonds is becoming a limiting factor in a number of die that may be included in a package. Additionally, forming a loop in the wire bonds increases the likelihood that one or more wire bonds can bend during fabrication and electrically short against the next adjacent wire bond.